Screen unit

ABSTRACT

A screen unit includes: a screen which has a first side and a second side opposing to each other in a first direction and extending substantially in parallel with each other; a first supporting portion extending along the first side to support the first side; a second supporting portion extending along the second side to support the second side; and a plurality of connecting mechanisms each of which extends between the first supporting portion and the second supporting portion, and expands and contracts in the first direction to move the second supporting portion close to and away from the first supporting portion, wherein the plurality of connecting mechanisms are disposed in parallel with the first supporting portion, and are located almost linearly symmetric with respect to a center line connecting approximately the center of the first side and approximately the center of the second side.

BACKGROUND

1. Technical Field

The present invention relates to a screen unit.

2. Related Art

A screen unit of a type currently known expands a screen on which animage is projected from a projection type display apparatus such as aprojector when the screen is used, and stores the screen when the screenis not used. This type of screen unit uses a pantograph-shapedconnecting mechanism in many cases which has a plurality of armsconnected with each other as a mechanism for shifting the screen upwardand downward at the time of expansion and storage of the screen and forsupporting the screen in an expanded condition.

An example known as a structure of this connecting mechanism has armsconnected in a rhomboidal shape and supporting the upper end portion ofthe screen at one point around the center of the screen. Also, such astructure which has arms crossing each other substantially in an X shapefor connection with each other and supporting two points of the upperend portion of the screen has been disclosed (For example, seeJP-A-5-34826). According to the screen unit shown in JP-A-5-34826, oneof the arms of the connecting mechanism is supported by a fixed supporton the upper end portion, and the other is supported by a movablesupport movable in the horizontal direction, in such a manner that therespective arms can freely rotate.

According to the structure which supports the upper end portion of thescreen at one point around the center of the screen, the left and rightends of the upper end portion of the screen easily bend in the downwarddirection, and the support for the screen easily becomes unstable.According to the structure of the screen unit shown in JP-A-5-34826which supports the upper end portion of the screen at the two points ofthe fixed support and the movable support, the supporting conditions atthe fixed support and the movable support differ from each other on theleft side and the right side. In this case, the movable support sidemore easily bends in the downward direction than the fixed support side,and the upper end portion of the screen easily shifts toward the fixedsupport side in the left-right direction.

According to this type of connecting mechanism, in most cases, theconnected arms cross each other while overlapping with each other atfront and rear positions in the normal line direction of the projectionsurface of the screen, and thus the arms constituting the connectingmechanism are not located on the same plane. In this arrangement, theconnecting mechanism is easily twisted by the load or the like generatedby the support of the upper end portion of the screen. As a result,relative twisting between the upper end portion and the lower endportion of the screen is easily produced.

The bend of the upper end portion of the screen, the shift of the upperend portion in the left-right direction, and the twist between the upperend portion and the lower end portion are more easily produced as thesize of the screen increases. These conditions decrease uniformity ofthe tension applied to the screen, and thus lowers the flatness of thescreen. Therefore, such a screen unit which can reduce lowering of theflatness of the screen even when the size of the screen enlarges hasbeen demanded.

SUMMARY

It is an advantage of some aspects of the invention to provide atechnology capable of solving at least a part of the problems describedabove and the invention can be embodied as the following forms orapplication examples.

Application Example 1

A screen unit according to this application example includes: a screenwhich has a first side and a second side disposed opposed to each otherand extending substantially in parallel with each other; a firstsupporting portion extending along the first side of the screen tosupport the first side; a second supporting portion extending along thesecond side of the screen to support the second side; and a plurality ofconnecting mechanisms each of which extends between the first supportingportion and the second supporting portion, and expands and contracts inthe direction in which the first supporting portion and the secondsupporting portion are opposed to move the second supporting portionclose to and away from the first supporting portion. The plurality ofconnecting mechanisms are disposed in parallel in the direction in whichthe first supporting portion and the second supporting portion extend,and are located almost linearly symmetric with respect to a center lineconnecting approximately the center of the first side in the extendingdirection of the first side and approximately the center of the secondside in the extending direction of the second side.

According to this structure, the screen is expanded when the secondsupporting portion is moved away from the first supporting portion inthe upward direction, for example, by using the plural connectingmechanisms. In the expanded condition of the screen, each of the firstsupporting portion and the second supporting portion is supported atplural points in its extending direction by the plural connectingmechanisms. Thus, bending of the second supporting portion positionedabove can be reduced. Moreover, since the plural connecting mechanismsare disposed almost linearly symmetric with respect to the center line,the first supporting portion and the second supporting portion aresupported approximately at symmetric positions in the left-rightdirection. Accordingly, in the expanded condition of the screen, atension applied to a left part of the screen and a tension applied to aright part of the screen become more uniform, and thus the flatness ofthe screen increases. Accordingly, the flatness of the screen does notlower even when the size of the screen enlarges.

Application Example 2

In the screen unit of the above application example, it is preferablethat the plural connecting mechanisms include a plurality of firstconnecting mechanisms disposed as a pair or pairs on both parts of thescreen unit with the center line interposed therebetween.

According to this structure, the plural first connecting mechanisms aredisposed as a pair or pairs on both parts of the screen unit with thecenter line interposed between the parts of the screen unit. Thus, thestrengths for supporting the first supporting portion and the secondsupporting portion become more uniform on the left and right parts inthe expanded condition of the screen. Thus, the flatness of the screenfurther increases.

Application Example 3

In the screen unit of the above application example, it is preferablethat the plural connecting mechanisms include a pair of the firstconnecting mechanisms, and that the pair of the first connectingmechanisms have almost linearly symmetric structures with respect to thecenter line as viewed in the normal line direction of a projectionsurface of the screen.

According to this structure, the pair of the first connecting mechanismshas almost linearly symmetric structures with respect to the centerline. Thus, even when twisting is produced on each of the firstconnecting mechanisms, the twisting can be cancelled by the firstconnecting mechanism as a paired unit. Accordingly, relative twistingbetween the first supporting portion and the second supporting portioncan be reduced, which further increases the flatness of the screen.

Application Example 4

It is preferable that the screen unit of the above application exampleis configured such that the first supporting portion includes a pair offixed supports provided at predetermined positions and a pair of movablesupports movable in the extending direction of the first supportingportion in correspondence with the pair of the first connectingmechanisms; the second supporting portion includes a pair of fixedsupports provided at predetermined positions and a pair of movablesupports movable in the extending direction of the second supportingportion in correspondence with the pair of the first connectingmechanisms; the respective first connecting mechanisms are connectedwith the respective fixed supports and the respective movable supportsof the first supporting portion and with the respective fixed supportsand the respective movable supports of the second supporting portion;and each pair of the fixed supports of the first supporting portion,each pair of the movable supports of the first supporting portion, eachpair of the fixed supports of the second supporting portion and eachpair of the movable supports of the second supporting portion aredisposed almost linearly symmetric with respect to the center line.

According to this structure, each pair of the fixed supports of thefirst supporting portion, each pair of the movable supports of the firstsupporting portion, each pair of the fixed supports of the secondsupporting portion and each pair of the movable supports of the secondsupporting portion are disposed almost linearly symmetric with respectto the center line. Thus, the restricting condition for each of the pairof the first connecting mechanisms becomes approximately the same on theleft and right parts. Accordingly, the supporting condition for each ofthe first supporting portion and the second supporting portion becomessubstantially equivalent to each other in the left part and in the rightpart, and thus bending and shift of the second supporting portion can bereduced.

Application Example 5

In the screen unit of the above application example, it is preferablethat the pair of the fixed supports of each of the first supportingportion and the second supporting portion are disposed outside the pairof the movable supports of the corresponding supporting portion withrespect to the center line.

According to this structure, the fixed supports are disposed outside themovable supports with respect to the center line. Thus, both outsideareas of each of the first supporting portion and the second supportingportion are supported at fixed positions in the expanded condition ofthe screen. As a result, bending at both ends of the second supportingportion in the left-right direction can be further reduced. Moreover,since the pair of the movable supports is disposed inside at positionsopposed to each other, a structure which moves the pair of the movablesupports by a single mechanism can be easily provided.

Application Example 6

It is preferable that the screen unit of the above application examplefurther includes a rotating mechanism which has a rotation shaftextending along the first supporting portion. In this case, each of thepair of the movable supports of the first supporting portion has a screwportion which has a female screw formed coaxially with each other. Therotation shaft is inserted through the screw portions of the pair of themovable supports of the first supporting portion and has a male screwengaging with the screw portions. One of the screw portions of the pairof the movable supports is a right-handed screw, and the other of thescrew portions of the pair of the movable supports is a left-handedscrew.

According to this structure, one of the screw portions of the pair ofthe movable supports is a right-handed screw, and the other of the screwportions of the pair of the movable supports is a left-handed screw.Thus, the pair of the movable supports shift in directions opposite toeach other along the extending direction of the first supporting portionin accordance with the rotation direction of the rotation shaft whichhas the male screw engaging with the screw portions. Thus, the pair ofthe connecting mechanisms can be expanded and contracted for expansionand storage of the screen by increasing and decreasing each distancebetween the fixed supports and the movable supports achieved through thechange of the rotation direction of the rotation shaft.

Application Example 7

It is preferable that the screen unit of the above application examplefurther includes a rotating mechanism which has a rotation shaftdisposed between the pair of the movable supports of the firstsupporting portion. In this case, one of the pair of the movablesupports is connected with the rotation shaft via a first wire, and theother of the pair of the movable supports is connected with the rotationshaft via a second wire. The first wire and the second wire are wound orreturned in accordance with the rotation direction of the rotation shaftto shift the pair of the movable supports in directions opposite to eachother along the first supporting portion.

According to this structure, the pair of the movable supports areshifted in directions opposite to each other along the extendingdirection of the first supporting portion in accordance with therotation direction of the rotation shaft by using the first wire and thesecond wire. Thus, the pair of the connecting mechanisms can be expandedand contracted for expansion and storage of the screen by increasing anddecreasing each distance between the fixed supports and the movablesupports achieved through the change of the rotation direction of therotation shaft.

Application Example 8

In the screen unit of the above application example, it is preferablethat the rotating mechanism has an electrically operated motor whichrotates the rotation shaft.

According to this structure, the pair of the connecting mechanisms canbe easily expanded and contracted by using the electrically operatedsystem to expand and contract the screen.

Application Example 9

In the screen unit of the above application example, it is preferablethat the plural connecting mechanisms further include a secondconnecting mechanism disposed on the center line.

According to this structure, the first supporting portion and the secondsupported portion are supported by the first connecting mechanisms andthe second connecting mechanism. Thus, bending of the second supportingportion can be more effectively reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 illustrates the general structure of a screen unit according to afirst embodiment.

FIGS. 2A and 2B illustrate the general structure of the screen unitaccording to the first embodiment.

FIGS. 3A through 3C illustrate a rotating mechanism according to thefirst embodiment.

FIG. 4 illustrates the general structure of a screen unit according to asecond embodiment.

FIG. 5 illustrates the general structure of a screen unit according to athird embodiment.

FIG. 6 illustrates the general structure of a screen unit according to afourth embodiment.

FIG. 7 illustrates the general structure of a screen unit according to afifth embodiment.

FIG. 8 illustrates the general structure of a screen unit according to asixth embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments according to the invention are hereinafterdescribed with reference to the drawings. In the figures to be referredto herein, the proportions, angles and the like of the sizes of therespective components and parts are varied as necessary for easyunderstanding of the structures.

First Embodiment

A screen unit according to a first embodiment is now described withreference to FIGS. 1, 2A and 2B, and 3A through 3C. FIGS. 1, 2A and 2Billustrate the general structure of the screen unit according to thefirst embodiment. More specifically, FIG. 1 schematically illustratesthe screen unit in an expanded condition as viewed from the back. FIG.2A schematically illustrates the screen unit in the expanded conditionas viewed from above. FIG. 2B schematically illustrates the screen unitin a stored condition as viewed from the back. FIGS. 3A through 3Cillustrate a rotating mechanism according to the first embodiment. Morespecifically, FIG. 3A is a perspective view showing the structure of amain part of the rotating mechanism, and FIGS. 3B and 3C illustrate theoperation of the rotating mechanism.

As illustrated in FIG. 1, a screen unit 1 according to the firstembodiment includes a screen 10, a storing portion 20 as a firstsupporting portion, a supporting portion 14 as a second supportingportion, a pair of connecting mechanisms 30 a and 30 b as firstconnecting mechanisms, and a rotating mechanism 40. The screen unit 1 isa screen unit including the screen 10 which is drawn out and expandedwhen the screen 10 is used, and is wound around a winding shaft 21 andstored in the storing portion 20 when the screen 10 is not used. In thisembodiment, a case in which the screen unit 1 is installed on a floorsurface shown as a crosshatched area in the figure will be discussed.

In the following explanation, the direction toward the floor surface onwhich the screen unit 1 is placed is referred to as the downwarddirection, and the direction toward the ceiling surface is referred toas the upward direction in some cases. In addition, the use condition ofthe screen unit 1 in which the screen 10 becomes substantially flat toform a projection surface is referred to as an expanded condition insome cases. In the expanded condition of the screen 10, the projectionside and the side opposite to the projection side are referred to as thefront side and the back side, respectively, in some cases. Also, theright side as viewed from the back and the left side as viewed from theback are referred to as the right and the left, respectively, in somecases. FIG. 1 shows the storing portion 20 in perspective.

The screen 10 is a reflection type screen having flexibility, andreflects image light projected from a projector or the like by aprojection surface on the front side to display an image, for example.The screen 10 has a side 11 as a first side and a side 12 as a secondside opposed to each other. The side 11 and the second side 12 extendsubstantially in parallel with each other. In the following explanation,the direction along the side 11 and the side 12 is referred to as an Xdirection in some cases. The side 11 is supported by the winding shaft21 included in the storing portion 20, and the side 12 is supported bythe supporting portion 14.

A center line CL indicated by an alternate long and short dash line is aline connecting the center of the side 11 in the X direction and thecenter of the side 12 in the X direction, and crosses the X directionapproximately at right angles. In the following explanation, a directionextending along the center line CL is referred to as a Z direction, anda direction crossing the X direction and the Z direction approximatelyat right angles is referred to as a Y direction in some cases. The planedefined by the X direction and the Y direction corresponds to a planesubstantially parallel with the floor surface as the installationsurface of the screen unit 1 (storing portion 20). The plane defined bythe X direction and the Z direction corresponds to a plane substantiallyparallel with the projection surface of the screen 10 in the expandedcondition. The Y direction extends substantially in parallel with anormal line N direction of the projection surface of the screen 10 (seeFIG. 2A).

The storing portion 20 is disposed on the floor surface side on whichthe screen unit 1 is installed, and extends in the X direction. Thestoring portion 20 has the winding shaft 21, a center shaft 22, atensioning mechanism (not shown), and bearings 23. The winding shaft 21is a cylindrical component extending in the X direction, and supportsthe side 11 of the screen 10. The winding shaft 21 is a shaft aroundwhich the screen 10 is wound. A pair of the bearings 23 are provided atboth ends of the winding shaft 21 in the X direction to support thewinding shaft 21 such that the winding shaft 21 can freely rotate.

The center shaft 22 is inserted into the winding shaft 21, and extendsin the X direction similarly to the winding shaft 21. The center shaft22 has the same rotation axis as that of the winding shaft 21, androtates in accordance with the rotation of the winding shaft 21. Thetensioning mechanism has a function of urging the center axis 22 in thedirection of winding the screen 10, and has known parts such as a springcoil.

When the winding shaft 21 (center shaft 22) is rotated in the directionin which the screen 10 is drawn out, an urging force for rotating thecenter shaft 22 in the direction of winding the screen 10 is generatedby the tensioning mechanism. Thus, when the screen 10 is expanded, thescreen 10 is tensioned in the up-down direction (Z direction) by theurging force of the tensioning mechanism. When the screen 10 is stored,the screen 10 is wound around the winding shaft 21 by the urging forceof the tensioning mechanism to be stored in the storing portion 20 (seeFIG. 2B).

The supporting portion 14 extends in the X direction and supports theside 12. A guide member 16 extending in the X direction is provided onthe supporting portion 14. The center line CL passes the center of thewinding shaft 21 in the X direction and the center of the supportingportion 14 in the X direction. Thus, the center line CL corresponds tothe center line of the screen unit 1.

The pair of the connecting mechanisms 30 a and 30 b extend between thestoring portion 20 and the supporting portion 14, and are equipped onthe back side of the screen 10. The connecting mechanisms 30 a and 30 bare so-called pantograph mechanisms. The connecting mechanism 30 a isdisposed on the right side with respect to the center line CL, and theconnecting mechanism 30 b is disposed on the left side with respect tothe center line CL. The connecting mechanisms 30 a and 30 b are locatedalmost linearly symmetrically with respect to the center line CL.

The connecting mechanism 30 a has two pairs of (four) arms 31 a, 32 a,33 a, and 34 a connected with each another. Each of the arms 31 a, 32 a,33 a, and 34 a is a pillar-shaped hollow component having a rectangularcross section, and has an equal length. The arms 31 a and 32 a aredisposed on the storing portion 20 side, and the arms 33 a and 34 a aredisposed on the supporting portion 14 side. The arms 31 a and 33 a arepositioned on the front side with respect to the arms 32 a and 34 a (seeFIG. 2A).

The arms 31 a and 32 a are disposed in such a manner as to cross eachother approximately in an X shape, and connected with each other by aconnecting portion 35 a positioned substantially at the centers of thearms 31 a and 32 a in such a manner as to be freely rotatable. The arms33 a and 34 a are disposed in such a manner as to cross each otherapproximately in an X shape, and connected with each other by theconnecting portion 35 a positioned substantially at the centers of thearms 33 a and 34 a in such a manner as to be freely rotatable similarlyto the arms 31 a and 32 a. The connected arms 31 a and 32 a and theconnected arms 33 a and 34 a are stacked in the up-down direction (Zdirection). The ends of the arm 31 a and the arm 34 a are connected by aconnecting portion 36 a, and the ends of the arm 32 a and the arm 33 aare similarly connected by the connecting portion 36 a, in such a manneras to be freely rotatable.

Similarly to the connecting mechanism 30 a, the connecting mechanism 30b has two pairs of (four) arms 31 b, 32 b, 33 b, and 34 b connected witheach another in such a manner as to be freely rotatable. The arms 31 b,32 b, 33 b, and 34 b and the arms 31 a, 32 a, 33 a, and 34 a aredisposed almost linearly symmetrically with respect to the center lineCL as viewed in the direction of the normal line N of the projectionsurface of the screen 10 (Y direction). Thus, the connecting mechanism30 a and the connecting mechanism 30 b have almost linearly symmetricstructures with respect to the center line CL as viewed in the directionof the normal line N of the projection surface of the screen 10.

The connecting mechanisms 30 a and 30 b expand and contract in theup-down direction (Z direction) by the stretch and bend of the armsconnected with one another. The expansion and contraction of theconnecting mechanisms 30 a and 30 b allows the supporting portion 14 toshift close to and away from the storing portion 20 (winding shaft 21)for expansion and storage of the screen 10. In the expanded condition ofthe screen 10, the connecting mechanisms 30 a and 30 b support thesupporting portion 14 above the storing portion 20. In the storedcondition of the screen 10, the connecting mechanisms 30 a and 30 b arefolded to store the screen 10 (see FIG. 2B).

The storing portion 20 has a pair of fixed supports 24 a and 24 b and apair of movable supports 26 a and 26 b in correspondence with the pairof the connecting mechanisms 30 a and 30 b. The fixed supports 24 a and24 b are fixed to predetermined positions of the storing portion 20. Themovable supports 26 a and 26 b are movable in the X direction. A screwportion having a female screw is formed on each of the movable supports26 a and 26 b coaxially in the X direction. The screw portions of themovable supports 26 a and 26 b engage with a rotation shaft 44 of therotating mechanism 40 described later.

The fixed support 24 a and the movable support 26 a associated with theconnecting mechanism 30 a are disposed on the right side with respect tothe center line CL. The fixed support 24 b and the movable support 26 bassociated with the connecting mechanism 30 b are disposed on the leftside with respect to the center line CL. The pair of the fixed support24 a and the movable support 26 a, and the pair of the fixed support 24b and the movable support 26 b are positioned almost linearlysymmetrically with respect to the center line CL. The fixed supports 24a and 24 b are located outside the movable supports 26 a and 26 b withrespect to the center line CL.

The end of the arm 32 a of the connecting mechanism 30 a is supported bythe fixed support 24 a in such a manner as to be freely rotatable, andthe end of the arm 31 a is supported by the movable support 26 a in sucha manner as to be freely rotatable. The end of the arm 32 b of theconnecting mechanism 30 b is supported by the fixed support 24 b in sucha manner as to be freely rotatable, and the end of the arm 31 b issupported by the movable support 26 b in such a manner as to be freelyrotatable.

A pair of fixed supports 17 a and 17 b and a pair of movable supports 18a and 18 b are provided on the supporting portion 14 in correspondencewith the pair of the connecting mechanisms 30 a and 30 b. The fixedsupports 17 a and 17 b are fixed to predetermined positions of thesupporting portion 14. The movable supports 18 a and 18 b are movable inthe X direction. More specifically, the guide member 16 has a guide holeextending in the X direction, and the movable supports 18 a and 18 bengage with the guide hole and freely slide within the guide hole in theX direction.

The fixed support 17 a and the movable support 18 a associated with theconnecting mechanism 30 a are disposed on the right side with respect tothe center line CL, and the fixed support 17 b and the movable support18 b associated with the connecting mechanism 30 b are disposed on theleft side with respect to the center line CL. The pair of the fixedsupport 17 a and the movable support 18 a, and the pair of the fixedsupport 17 b and the movable support 18 b are positioned almost linearlysymmetrically with respect to the center line CL. The fixed supports 17a and 17 b are disposed outside the movable supports 18 a and 18 b withrespect to the center line CL.

The end of the arm 33 a of the connecting mechanism 30 a is supported bythe fixed support 17 a in such a manner as to be freely rotatable, andthe end of the arm 34 a is supported by the movable support 18 a in sucha manner as to be freely rotatable. The end of the arm 33 b of theconnecting mechanism 30 b is supported by the fixed support 17 b in sucha manner as to be freely rotatable, and the end of the arm 34 b issupported by the movable support 18 b in such a manner as to be freelyrotatable.

According to the screen unit 1 which includes the connecting mechanisms30 a and 30 b connected with the storing portion 20 and the supportingportion 14, the storing portion 20 and the supporting portion 14 aresupported at four points in the expanded condition of the screen 10.Thus, bending of the supporting portion 14 located on the upper side canbe reduced. Moreover, since the connecting mechanisms 30 a and 30 b aredisposed almost linearly symmetrically with respect to the center lineCL, the storing portion 20 and the supporting portion 14 are supportedapproximately at the symmetric positions in the left-right direction.Accordingly, in the expanded condition of the screen 10, the strengthsfor supporting the storing portion 20 and the supporting portion 14become almost uniform in the left-right direction, and thus a tensionapplied to a left part of the screen 10 and a tension applied to a rightpart of the screen 10 become more uniform.

In case of a structure which includes only the connecting mechanism 30 awith the connecting portions 35 a located on the center line CL in theexpanded condition of the screen 10 as the screen unit disclosed inJP-A-5-34826, the supporting portion 14 is supported at the two pointsof the fixed support 17 a and the movable support 18 a. Since themovable support 18 a freely slides in contrast with the fixed support 17a fixed to a predetermined position, the restricting conditions for thearms 33 a and 34 a of the connecting mechanism 30 a differ from eachother. Accordingly, the supporting conditions for the two points of thesupporting portion 14 differ from each other.

In this case, the supporting portion 14 on the movable support 18 a sidemore easily bends downward than on the fixed support 17 a side, and thesupporting portion 14 easily shifts toward the fixed support 17 a in theleft-right direction (X direction). The bend and shift produced on thesupporting portion 14 causes the screen 10 to be tensioned non-uniformlyand produces distortion and bend on the screen 10. In this case,problems such as deterioration of the quality of images projected on theprojection surface of the screen 10, and shift of image projection froma desired projection position on the screen 10 arise.

According to the screen unit 1, however, the pair of the fixed support17 a and the movable support 18 a and the pair of the fixed support 17 band the movable support 18 b are disposed substantially symmetrically inthe left-right direction. Thus, the restricting conditions for theconnecting mechanisms 30 a and 30 b are approximately the same.Accordingly, the supporting condition for the supporting portion 14 inthe left part and the supporting condition for the supporting portion 14in the right part becomes approximately the same. Moreover, the fixedsupports 17 a and 17 b are disposed outside the movable supports 18 aand 18 b with respect to the center line CL. Thus, both the outsideareas of the supporting portion 14 in the left-right direction can befixed and supported with stability. Accordingly, a tension applied tothe left part of the screen 10 and a tension applied to the right partof the screen 10 become more uniform, and bending of the supportingportion 14 on one side and shift of the supporting portion 14 in theleft-right direction (X direction) can be both reduced.

As illustrated in FIG. 2A, the respective arms 31 a through 34 a of theconnecting mechanism 30 a are disposed in such conditions that the arms31 a and 33 a cross and overlap with the arms 32 a and 34 a in thefront-rear direction, respectively, as viewed in the normal line Ndirection of the screen 10. The arms 31 b and 33 b and the arms 32 b and34 b of the connecting mechanism 30 b are disposed in a similar manner.

According to a typical connecting mechanism whose plural arms cross andconnect with each other, the arms constituting the connecting mechanismare not located on the same plane. In this case, twisting is easilyproduced by the load or the like generated by the support of the upperend portion of the screen. In case of the structure of the screen unitwhich includes only the connecting mechanism 30 a extending between thestoring portion 20 and the supporting portion 14 as disclosed inJP-A-5-34826, the twist generated on the connecting mechanism 30 a leadsto relative twisting between the storing portion 20 and the supportingportion 14.

According to the screen unit 1, however, the connecting mechanisms 30 aand 30 b are provided as almost linearly symmetric structures withrespect to the center line CL as viewed in the direction of the normalline N of the projection surface of the screen 10. Thus, even whentwisting is generated on each of the connecting mechanisms 30 a and 30b, the generated twists can be cancelled by each other due to thestructure of the connecting mechanisms 30 a and 30 b substantiallysymmetric in the left-right direction. Accordingly, the relativetwisting between the storing portion 20 and the supporting portion 14can be reduced.

According to the screen unit 1, therefore, a tension applied to the leftpart of the screen 10 and a tension applied to the right part of thescreen 10 become more uniform, and generation of bend and shift of thescreen 10 can be reduced. Thus, the flatness of the screen 10 increases,and does not decrease even when the size of the screen 10 enlarges.Accordingly, deterioration of the quality of the images projected on theprojection surface of the screen 10 can be avoided.

The rotating mechanism 40 is now explained. As illustrated in FIG. 1,the rotating mechanism 40 is disposed on the back side and on thestoring portion 20 side of the screen 10. The rotating mechanism 40includes an electrically operated motor 42, the rotation shaft 44, malescrews 46 a and 46 b formed on the rotation shaft 44, and bearings 48.The electrically operated motor 42 is fixed to the storing portion 20.The electrically operated motor 42 rotates the rotation shaft 44.

The rotation shaft 44 extending in the X direction is threaded throughthe screw portion formed on the movable support 26 a on the connectingmechanism 30 a side, and the screw portion formed on the movable support26 b on the connecting mechanism 30 b side. The bearings 48 are providedat both ends of the rotation shaft 44 in the extending direction of therotation shaft 44 and approximately at the center of the rotation shaft44 to support the rotation shaft 44 such that the rotation shaft 44 canfreely rotate.

As illustrated in FIGS. 3A, 3B, and 3C, the screw portion formed on themovable support 26 a associated with the connecting mechanism 30 aengages with the male screw 46 a formed on the rotation shaft 44. Asillustrated in FIGS. 3B and 3C, the screw portion formed on the movablesupport 26 b associated with the connecting mechanism 30 b engages withthe male screw 46 b formed on the rotation shaft 44.

The screw portion formed on the movable support 26 a is a left-handedscrew, and the screw portion formed on the movable support 26 b is aright-handed screw. The screw portions formed on the movable supports 26a and 26 b have substantially the same pitch. The male screw 46 a isformed on the rotation shaft 44 on the movable support 26 a side withrespect to the center line CL, and the male screw 46 b is formed on therotation shaft 44 on the movable support 26 b side with respect to thecenter line CL. The male screw 46 a is a left-handed screw, and the malescrew 46 b is a right-handed screw. The male screws 46 a and 46 b haveapproximately the same pitch. When the rotation shaft 44 is rotated in apredetermined rotation direction in this structure, the movable supports26 a and 26 b are shifted in directions opposite to each other along theX direction in accordance with the rotation direction of the rotationshaft 44.

When the rotation shaft 44 is rotated anticlockwise as viewed from theelectrically operated motor 42, for example, in the stored condition ofthe screen 10 (see FIG. 2B) as illustrated in FIG. 3B, each of themovable supports 26 a and 26 b shifts in a direction away from thecenter line CL. As a result, the end of the arm 31 a supported by themovable support 26 a and the end of the arm 31 b supported by themovable support 26 b shift outward on both sides with respect to thecenter line CL. In this condition, the distance between the end of thearm 31 a (movable support 26 a) and the end of the arm 32 a (fixedsupport 24 a) decreases on the connecting mechanism 30 a side, and thedistance between the end of the arm 31 b (movable support 26 b) and theend of the arm 32 b (fixed support 24 b) decreases on the connectingmechanism 30 b side.

In accordance with this movement, the movable supports 18 a and 18 b onthe supporting portion 14 side slide along the guide member 16 and shiftin directions away from the center line CL. In this condition, thedistance between the end of the arm 34 a (movable support 18 a) and theend of the arm 33 a (fixed support 17 a) decreases on the connectingmechanism 30 a side, and the distance between the end of the arm 34 b(movable support 18 b) and the end of the arm 33 b (fixed support 17 b)decreases on the connecting mechanism 30 b side. As a result, theconnecting mechanisms 30 a and 30 b expand upward, thereby separatingthe supporting portion 14 from the storing portion 20 (winding shaft 21)for expansion of the screen 10 and tensioning the screen 10 in theup-down direction.

When the rotation of the rotation shaft 44 by using the electricallyoperated motor 42 is stopped in this condition, the movable supports 26a and 26 b having the screw portions engaging with the male screws 46 aand 46 b stop moving at the positions at which the rotation of therotation shaft 44 is suspended. Thus, the screen 10 (supporting portion14) can be maintained at a desired height by controlling the positionsof the movable supports 26 a and 26 b.

When the rotation shaft 44 is rotated clockwise as viewed from theelectrically operated motor 42, for example, in the expanded conditionof the screen 10 (see FIG. 1) as illustrated in FIG. 3C, each of themovable supports 26 a and 26 b shifts toward the center line CL. As aresult, the distance between the end of the arm 31 a (movable support 26a) and the end of arm 32 a (fixed support 24 a), and the distancebetween the end of the arm 34 a (movable support 18 a) and the end ofthe arm 33 a (fixed support 17 a) on the connecting mechanism 30 a sideincrease as illustrated in FIG. 2B.

Similarly, the distance between the end of the arm 31 b (movable support26 b) and the end of the arm 32 b (fixed support 24 b), and the distancebetween the end of the arm 34 b (movable support 18 b) and the end ofthe arm 33 b (fixed support 17 b) on the connecting mechanism 30 b sideincrease. As a result, the connecting mechanisms 30 a and 30 b arefolded downward, and the screen 10 is stored in the storing portion 20by movement of the supporting portion 14 closer to the storing portion20 (winding shaft 21).

Since the screw portions of the movable supports 26 a and 26 b haveapproximately the same pitch, the movement distances of the respectivemovable supports 26 a and 26 b for the number of revolutions of therotation shaft 44 are substantially equivalent. In this case, the pairof the connecting mechanisms 30 a and 30 b can be expanded andcontracted approximately with synchronization, and thus the screen 10can be supported substantially in the symmetric condition in theleft-right direction regardless of the expanding and contractingconditions of the connecting mechanisms 30 a and 30 b. Accordingly, atension applied to the left part of the screen 10 and a tension appliedto the right part of the screen 10 become more uniform, and can beexpanded and stored in a stable condition.

According to the screen unit 1, the movable supports 26 a and 26 b ofthe storing portion 20 are positioned inside the fixed supports 24 a and24 b. Thus, the structure which expands and contracts the pair of theconnecting mechanisms 30 a and 30 b by using the one rotating mechanism40 can be easily produced. Therefore, the screen 10 can be expanded andstored in a stable condition by a simple structure using electric powerwithout requiring a large-scale mechanism.

The guide member 16 provided on the supporting portion 14 may bereplaced with a rail member engaging with the movable supports 18 a and18 b such that the movable supports 18 a and 18 b can freely slidewithin the rail member in the X direction. The guide member or railmember engaging with the movable supports 26 a and 26 b such that themovable supports 26 a and 26 b can freely slide within the guide memberor rail member in the X direction may also be provided on the storingportion 20. In addition, a cover or the like for storing the respectivecomponents of the screen unit 1 in the storing portion 20 when thescreen unit 1 is not used may be provided on the storing portion 20.

According to the structure of the screen unit 1 in the first embodiment,the following advantages can be offered.

(1) The storing portion 20 and the supporting portion are supported atplural positions by the connecting mechanisms 30 a and 30 b. Thus,bending of the supporting portion 14 can be reduced.

(2) The storing portion 20 and the supporting portion 14 are supportedby the connecting mechanisms 30 a and 30 b substantially with symmetryin the left-right direction. Thus, the strengths for supporting thestoring portion 20 and the supporting portion 14 become more uniform inthe left-right direction.

(3) The supporting conditions for the storing portion 20 and thesupporting portion 14 become substantially equivalent in the left-rightdirection. Thus, bend and shift of the supporting portion 14 can bereduced.

(4) The connecting mechanisms 30 a and 30 b have almost linearlysymmetric structures with respect to the center line CL. In this case,twisting of the connecting mechanisms 30 a and 30 b can be cancelled byeach other, and thus relative twisting between the storing portion 20and the supporting portion 14 can be reduced.

As a result, a tension applied to the left part of the screen 10 and atension applied to the right part of the screen 10 become more uniform,which increases the flatness of the screen 10. Accordingly, the flatnessof the screen 10 does not lower even when the size of the screen 10enlarges.

(5) The storing portion 20 and the supporting portion 14 are supportedapproximately with symmetry in the left-right direction regardless ofthe degree of expansion of the screen 10 (the height of the supportingportion 14 with respect to the storing portion 20). Thus, the screen 10can be expanded and stored in a stable condition.

(6) The pair of the movable supports 26 a and 26 b are disposed insideat positions opposed to each other. Thus, the connecting mechanisms 30 aand 30 b can be expanded and contracted by using a simple structureincluding the rotating mechanism 40 such that the screen 10 can beexpanded and stored by electrical power.

While the screen unit 1 placed on the floor surface has been discussedin this embodiment, the screen unit 1 may be installed on the ceilingsurface. When the screen unit 1 is disposed on the ceiling surface, thestoring portion 20 is positioned on the ceiling surface side. In thiscase, the positions of the connecting mechanisms 30 a and 30 b, thesupporting portion 14 and others with respect to the storing portion 20are reversed in the up-down direction. Also, the gravity acts in thedirection of expanding the screen 10. Thus, the screen 10 can beexpanded and stored by drawing the connecting mechanisms 30 a and 30 bdownward from the storing portion 20 located on the ceiling surface sideand contracting and folding the connecting mechanisms 30 a and 30 bupward toward the storing portion 20. When the screen unit 1 isinstalled on the ceiling surface for use, the screen 10 can be tensionedin the up-down direction by increasing the weight of the supportingportion 14.

Second Embodiment

A screen unit according to a second embodiment is now described withreference to the drawings. FIG. 4 illustrates the general structure ofthe screen unit in the second embodiment. More specifically, FIG. 4schematically illustrates a main part of the screen unit as viewed fromthe back.

The screen unit in the second embodiment has a structure similar to thatof the screen unit in the first embodiment except for the structure ofthe rotating mechanism. Common reference numbers are given to parts andcomponents common to those in the first embodiment, and the sameexplanation of the common parts and components is not repeated.

The structure of a screen unit 2 according to the second embodiment isnow explained with reference to FIG. 4. The screen unit 2 in the secondembodiment is a screen unit installed on the floor surface. The screenunit 2 includes the screen 10 (see FIG. 1), the storing portion 20, thesupporting portion 14 (see FIG. 1), a pair of the connecting mechanisms30 a and 30 b, and a rotating mechanism 50A. The rotating mechanism 50Ahas a structure appropriate for installation on a floor surface.

The fixed supports 24 a and 24 b (see FIG. 1) and movable supports 28 aand 28 b are provided on the storing portion 20 in correspondence withthe connecting mechanisms 30 a and 30 b. The end of the arm 31 a issupported by the movable support 28 a such that the arm 31 a can freelyrotate. The end of the arm 31 b is supported by the movable support 28 bsuch that the arm 31 b can freely rotate. A guide member 27 extending inthe X direction is further provided on the storing portion 20. The guidemember 27 has a guide hole extending in the X direction, and the movablesupports 28 a and 28 b engage with the guide hole in such a manner as tofreely slide within the guide hole in the X direction.

The rotating mechanism 50A has the electrically operated motor 42 (seeFIG. 1), the rotation shaft 44, a rotation shaft 54, a wire 58 a as afirst wire, a wire 58 b as a second wire, and pulleys 59 a and 59 b. Aworm gear 45 is equipped on the rotation shaft 44.

The rotation shaft 54 is supported by a supporting member 52 providedbetween the movable support 28 a and the movable support 28 b. Therotation shaft 54 extends in the Y direction. That is, the rotationshaft 54 crosses the rotation shaft 44 approximately at right angles. Aspur gear 56 engaging with the worm gear 45 by screw engagement isprovided on the rotation shaft 54. Thus, the rotation of the rotationshaft 44 is transmitted to the rotation shaft 54 via the worm gear 45and the spur gear 56.

The pulley 59 a is disposed outside (on the right side of) the movablesupport 28 a with respect to the center line CL, and the pulley 59 b isdisposed outside (on the left side of) the movable support 28 b withrespect to the center line CL. The pulleys 59 a and 59 b are attached tocorresponding shafts provided on the storing portion 20 and having axialdirections extending in the Y direction.

One end of the wire 58 a is connected with the movable support 28 a, andthe other end of the wire 58 a is connected with the rotation shaft 54.One end of the wire 58 b is connected with the movable support 28 b, andthe other end of the wire 58 b is connected with the rotation shaft 54.Thus, the movable supports 28 a and 28 b are connected with the rotationshaft 54 via the wires 58 a and 58 b. The wire 58 a is wound around thepulley 59 a between the movable support 28 a and the rotation shaft 54,and the wire 58 b is wound around the pulley 59 b between the movablesupport 28 b and the rotation shaft 54.

When the rotation shaft 54 is rotated in a predetermined rotationdirection in the stored condition of the screen 10 (see FIG. 2B), theends of the wires 58 a and 58 b connected with the rotation shaft 54 areinitially wound. The lengths of the wires 58 a and 58 b wound per onerotation of the rotation shaft 54 are equal to each other. By winding ofthe wires 58 a and 58 b around the rotation shaft 54, the movablesupport 28 a (end of the arm 31 a) connected with the wire 58 a and themovable support 28 b (end of the arm 31 b) connected with the wire 58 bshift toward the pulleys 59 a and 59 b, that is, outward on both sideswith respect to the center line CL by pulling forces given from thewires 58 a and 58 b.

As a result, the distance between the ends of the arm 31 a and the arm32 a of the connecting mechanism 30 a and the distance between the endsof the arm 31 b and the arm 32 b of the connecting mechanism 30 b (seeFIG. 1) decrease, and thus the connecting mechanisms 30 a and 30 bstretch upward. Therefore, the screen 10 expands by separation of thesupporting portion 14 from the storing portion 20.

According to the screen unit 2 installed on the floor surface, thegravity acts in the direction of moving the supporting portion 14downward (toward the floor surface), that is, in the direction offolding the connecting mechanisms 30 a and 30 b. The screen 10 of thescreen unit 2 is maintained in the expanded condition by the pullingforces given from the wires 58 a and 58 b by the engagement between theworm gear 45 and the spur gear 56 while resisting the gravity. Othercomponents such as a mechanism for preventing reverse rotations of theworm gear 45 and the spur gear 56 in the expanded condition of thescreen 10 may be added as necessary.

For storing the screen 10, the rotation shaft 54 around which the wires58 a and 58 b are wound is rotated in the opposite direction to returnthe wires 58 a and 58 b wound around the rotation shaft 54 to theinitial positions. In this case, the gravity acts in the direction ofmoving the supporting portion 14 downward, and thus the movable supports28 a and 28 b shift toward the center line CL by the lengths ofreturning the wires 58 a and 58 b, allowing the connecting mechanisms 30a and 30 b to be folded. As a result, the supporting portion 14 comesclose to the storing portion 20, allowing the screen 10 to be stored inthe storing portion 20.

According to the screen unit 2 in the second embodiment, therefore, therespective wires 58 a and 58 b are wound or returned in accordance withthe rotation direction of the rotation shaft 54, and the ends of thearms 31 a and 31 b shift in directions opposite to each other along theX direction. By this method, the screen unit 2 can expand and store thescreen 10 by expanding and contracting the connecting mechanisms 30 aand 30 b in the similar manner. The screen unit 2 in the secondembodiment can provide advantages similar to those of the screen unit 1in the first embodiment.

Each of the worm gear 45 provided on the rotation shaft 44 and the spurgear 56 provided on the rotation shaft 54 included in the screen unit 2in the second embodiment may be replaced with a bevel gear.

Third Embodiment

A screen unit according to a third embodiment is now described withreference to the drawings. FIG. 5 illustrates the general structure ofthe screen unit in the third embodiment. More specifically, FIG. 5schematically illustrates a main part of the screen unit as viewed fromthe back.

The screen unit in the third embodiment has substantially the samestructure as that of the screen unit in the second embodiment except fora rotating mechanism suited for installation on the ceiling surface.Common reference numbers are given to parts and components common tothose in the second embodiment, and the same explanation of the commonparts and components is not repeated.

The structure of a screen unit 3 according to the third embodiment isnow explained. The screen unit 3 in the third embodiment is a screenunit installed on the ceiling surface. The screen unit 3 includes thescreen 10 (see FIG. 1), the storing portion 20, the supporting portion14 (see FIG. 1), a pair of the connecting mechanisms 30 a and 30 b, anda rotating mechanism 50B. The rotating mechanism 50B has a structureappropriate for installation on the ceiling surface.

The rotating mechanism 50B includes the electrically operated motor 42(see FIG. 1), the rotation shaft 44, the rotation shaft 54, and thewires 58 a and 58 b. The movable supports 28 a and 28 b are connectedwith the rotation shaft 54 via the wires 58 a and 58 b. When the wires58 a and 58 b are wound around the rotation shaft 54, the movablesupport 28 a (the end of the arm 31 a) and the movable support 28 b (theend of the arm 31 b) shift toward the center line CL.

According to the screen unit 3 installed on the ceiling surface, thegravity acts in the direction of moving the supporting portion 14downward from the ceiling surface, that is, in the direction ofexpanding the connecting mechanisms 30 a and 30 b. Thus, for storing thescreen 10 in the storing portion 20, the connecting mechanisms 30 a and30 b are contracted upward and folded against the gravity.

According to the screen unit 3, the distance between the arm 31 a andthe arm 32 a of the connecting mechanism 30 a and the distance betweenthe arm 31 b and the arm 32 b of the connecting mechanism 30 b (seeFIG. 1) increase by winding the wires 58 a and 58 b around the rotationshaft 54. As a result, the connecting mechanisms 30 a and 30 b arefolded upward, and thus the screen 10 is stored.

When the rotation shaft 54 around which the wires 58 a and 58 b arewound is rotated in the opposite direction, the wires 58 a and 58 bwound around the rotation shaft 54 return to the initial positions. Inthis case, the gravity acts in the direction of moving the supportingportion 14 downward, and thus the movable supports 28 a and 28 b shiftoutward on both sides with respect to the center line CL by the lengthsof returning the wires 58 a and 58 b, allowing the connecting mechanisms30 a and 30 b to expand downward. As a result, the screen 10 is expandedby the downward expansion of the connecting mechanisms 30 a and 30 b.

According to the screen unit 3 in the third embodiment, therefore, therespective wires 58 a and 58 b are wound or returned in accordance withthe rotation direction of the rotation shaft 54, and the ends of thearms 31 a and 31 b shift in directions opposite to each other along theX direction similarly to the screen unit 2 in the second embodiment.Thus, the screen unit 3 can expand and store the screen 10 by expandingand contracting the connecting mechanisms 30 a and 30 b in the similarmanner. The screen unit 3 in the third embodiment can provide advantagessimilar to those of the screen unit 2 in the second embodiment.

Fourth Embodiment

A screen unit according to a fourth embodiment is now described withreference to the drawings. FIG. 6 illustrates the general structure ofthe screen unit in the fourth embodiment. More specifically, FIG. 6schematically illustrates the screen unit in the expanded condition asviewed from the back.

The screen unit in the fourth embodiment has substantially the samestructure as that of the screen unit in the first embodiment except thatthe connecting mechanisms are manually expanded and contracted. Commonreference numbers are given to parts and components common to those inthe first embodiment, and the same explanation of the common parts andcomponents is not repeated.

As illustrated in FIG. 6, the screen unit 4 in the fourth embodimentincludes the screen 10, the storing portion 20, the supporting portion14, and a pair of connecting mechanisms 60 a and 60 b as firstconnecting mechanisms. The connecting mechanisms 60 a and 60 b extendbetween the storing portion 20 and the supporting portion 14, and aredisposed on the back side of the screen 10. The connecting mechanisms 60a and 60 b are positioned almost linearly symmetrically with respect tothe center line CL, and have almost linearly symmetric structures withrespect to the center line CL.

The connecting mechanism 60 a has three pairs of (six) arms 61 a, 62 a,63 a, 64 a, 65 a, and 66 a connected with one another. The arms 63 a and64 a are disposed in such a manner as to cross each other approximatelyin an X shape. The ends of the arms 63 a and 64 a on the storing portion20 side are connected with the arms 61 a and 62 a, and the ends of thearms 63 a and 64 a on the supporting portion 14 side are connected withthe arms 65 a and 66 a. The ends of the arms 61 a and 62 a on thestoring portion 20 side are connected with each other and supported by afixed support 29 a provided on the storing portion 20 such that the arms61 a and 62 a can freely rotate. The ends of the arms 65 a and 66 a onthe supporting portion 14 side are connected with each other andsupported by a fixed support 19 a provided on the support portion 14such that the arms 65 a and 66 a can freely rotate.

The connecting mechanism 60 b has three pairs of (six) arms 61 b, 62 b,63 b, 64 b, 65 b, and 66 b having similar structures as those of thearms 61 a through 66 a of the connecting mechanism 60 a. The ends of thearms 61 b and 62 b on the storing portion 20 side are connected witheach other and supported by a fixed support 29 b provided on the storingportion 20 such that the arms 61 b and 62 b can freely rotate. The endsof the arms 65 b and 66 b on the supporting portion 14 side areconnected with each other and supported by a fixed support 19 b providedon the support portion 14 such that the arms 65 b and 66 b can freelyrotate.

A pair of springs (gas springs or coil springs) 68 a and 69 a areprovided between the arms 63 a and 64 a of the connecting mechanism 60a, and a pair of springs 68 b and 69 b are provided between the arms 63b and 64 b of the connecting mechanism 60 b. According to the screenunit 4, the connecting mechanisms 60 a and 60 b are manually expandedand contracted for expansion and storage of the screen 10, and theheight of the supporting portion 14 of the screen 10 is maintained byusing pressures or elastic forces of the springs 68 a, 69 a and 68 b, 69b.

In case of a structure which has only the connecting mechanism 60 alocated on the center line CL, each of the storing portion 20 and thesupporting portion 14 is supported at one point. In this case, bendingis easily produced at both ends of the supporting portion 14 in theleft-right direction, and also shift and twisting are easily generated.

According to the screen unit 4, however, the connecting mechanisms 60 aand 60 b are disposed almost linearly symmetrically with respect to thecenter line CL. Thus, each of the storing portion 20 and the supportingportion 14 is supported at two points substantially symmetric in theleft-right direction. Moreover, the connecting mechanisms 60 a and 60 bhave almost linearly symmetric structures with respect to the centerline CL. Thus, respective twists of the connecting mechanisms 60 a and60 b are canceled by each other. Accordingly, bend, shift, and twistingof the screen 10 decrease, which increases the flatness of the screen10.

Fifth Embodiment

A screen unit according to a fifth embodiment is now described withreference to the drawings. FIG. 7 illustrates the general structure ofthe screen unit in the fifth embodiment. More specifically, FIG. 7schematically illustrates the screen unit in the expanded condition asviewed from the back.

The screen unit in the fifth embodiment has substantially the samestructure as that of the screen unit in the first embodiment except thata second connecting mechanism is provided in addition to the firstconnecting mechanisms. Common reference numbers are given to parts andcomponents common to those in the first embodiment, and the sameexplanation of the common parts and components is not repeated.

As illustrated in FIG. 7, the screen unit 5 in the fifth embodimentincludes the screen 10, the storing portion 20, the supporting portion14, a pair of the connecting mechanisms 30 a and 30 b as the firstconnecting mechanisms, a connecting mechanism 60 as the secondconnecting mechanism, and the rotating mechanism 40.

The screen 10 of the screen unit 5 has a larger width in the left-rightdirection (X direction) than each width of the screen units 1, 2, 3, and4 in the above embodiments. Thus, the lengths of the storing portion 20and the supporting portion 14 in the left-right direction (X direction)are larger than those of the screen units 1, 2, 3, and 4 in the aboveembodiments. According to the screen unit 5, the connecting mechanisms30 a and 30 b are main connecting mechanisms, and the connectingmechanism 60 is a supplementary connecting mechanism for the connectingmechanisms 30 a and 30 b.

The distance between the connecting mechanisms 30 a and 30 b is largerthan that of the screen unit 1 in the first embodiment. The connectingmechanism 60 has a structure similar to that of the connecting mechanism60 a or the connecting mechanism 60 b in the fourth embodiment, forexample. The connecting mechanism 60 is disposed on the center line CLin the area between the connecting mechanisms 30 a and 30 b, and isconnected with a fixed support 29 provided on the storing portion 20 anda fixed support 19 provided on the supporting portion 14.

The respective positions of the connecting mechanism 60, the fixedsupport 29, and the fixed support 19 in the X direction and the Ydirection are determined in such positions as not to interfere with theconnecting mechanisms 30 a and 30 b and the rotating mechanism 40.According to the screen unit 5, the connecting mechanisms 30 a and 30 bare expanded and contracted by electric power for expansion and storageof the screen 10, and the connecting mechanism 60 is also expanded andcontracted in accordance with the movements of the connecting mechanisms30 a and 30 b.

When the width of the screen 10 in the left-right direction (Xdirection) is increased without adding the connecting mechanism 60 andwithout changing the positions of the connecting mechanisms 30 a and 30b from those of the screen unit 1 in the first embodiment, bending iseasily produced at both ends of the supporting portion 14 in theleft-right direction. When the distance between the connectingmechanisms 30 a and 30 b is enlarged, bending is easily produced at thecenter of the supporting portion 14.

According to the screen unit 5, both ends of each of the storing portion20 and the supporting portion 14 in the left-right direction aresupported substantially at symmetric positions in the left-rightdirection by the connecting mechanisms 30 a and 30 b, and the center ofeach of the storing portion 20 and the supporting portion 14 issupported by the connecting mechanism 60. Thus, even when the width ofthe screen 10 in the left-right direction (X direction) increases,bending at both ends of the supporting portion 14 in the left-rightdirection and the center of the supporting portion 14 decreases. Thus,the flatness of the screen 10 increases.

According to the screen unit 5 in the fifth embodiment, therefore, theflatness of the screen 10 does not lower even when the screen unit has aso-called wide projection surface whose ratio of the length in thehorizontal direction (X direction) to the length in the verticaldirection (Z direction) is larger.

In the screen unit 5, the rotating mechanism 40 may be replaced with therotating mechanism 50A in the second embodiment or the rotatingmechanism 50B in the third embodiment.

Sixth Embodiment

A screen unit according to a sixth embodiment is now described withreference to the drawings. FIG. 8 illustrates the general structure ofthe screen unit in the sixth embodiment. More specifically, FIG. 8schematically illustrates the screen unit in the expanded condition asviewed from the back.

The screen unit in the sixth embodiment has substantially the samestructure as that of the screen unit in the first embodiment except thattwo pairs of connecting mechanisms are provided as the first connectingmechanisms. Common reference numbers are given to parts and componentscommon to those in the first embodiment, and the same explanation of thecommon parts and components is not repeated.

As illustrated in FIG. 8, the screen unit 6 in the sixth embodimentincludes the screen 10, the storing portion 20, the supporting portion14, two pairs of connecting mechanisms 30 a, 30 b, 30 c and 30 d as thefirst connecting mechanisms, and rotating mechanisms 40 a and 40 b.According to the screen unit 6, the width of the screen 10 in theleft-right direction (X direction) is further larger than that of thescreen 5 in the fifth embodiment.

The connecting mechanisms 30 a and 30 b are disposed on the right sidewith respect to the center line CL, and the connecting mechanisms 30 cand 30 d are disposed on the left side with respect to the center lineCL. The connecting mechanisms 30 a and 30 b are located almost linearlysymmetrically with respect to a center line CLa positioned approximatelyat the center between the connecting mechanisms 30 a and 30 b, and havealmost linearly symmetric structures with respect to the center lineCLa. The connecting mechanisms 30 c and 30 d are located almost linearlysymmetrically with respect to a center line CLb positioned approximatelyat the center between the connecting mechanisms 30 c and 30 d, and havealmost linearly symmetric structures with respect to the center lineCLb.

Moreover, the connecting mechanisms 30 a and 30 d are located almostlinearly symmetrically with respect to the center line CL, and havealmost linearly symmetric structures with respect to the center line CL.The connecting mechanisms 30 b and 30 c are located almost linearlysymmetrically with respect to the center line CL, and have almostlinearly symmetric structures with respect to the center line CL. Thecenter line CLa and the center line CLb are disposed almost linearlysymmetrically with respect to the center line CL. The center line CLamay agree with a line connecting the center of the right part of theside 11 and the center of the right part of the side 12 with respect tothe center line CL. Similarly, the center line CLb may agree with a lineconnecting the center of the left part of the side 11 and the center ofthe left part of the side 12 with respect to the center line CL.

According to the screen unit 6, therefore, the pair of the connectingmechanisms 30 a and 30 b are disposed as one of a pair on the rightside, and the pair of the connecting mechanisms 30 c and 30 d aredisposed as the other of the pair on the left side with the center lineCL interposed therebetween. In another point of view, the pair of theconnecting mechanisms 30 a and 30 d are disposed as a pair on the rightside and the left side, and the pair of the connecting mechanisms 30 band 30 c are disposed as a pair on the right side and the left side withthe center line CL interposed between each pair.

According to the screen unit 6, both the right parts and the left partsof the storing portion 20 and the supporting portion 14 are supported bythe connecting mechanisms 30 a and 30 b and the connecting mechanisms 30c and 30 d substantially at the symmetric positions in the left-rightdirection and substantially in the same supporting conditions. Thus,even when the width of the screen 10 in the left-right direction (Xdirection) further increases, bending at both ends of the supportingportion 14 in the left-right direction and at the center of thesupporting portion 14 can be reduced. Thus, the flatness of the screen10 improves.

Each of the rotating mechanisms 40 a and 40 b has a structure similar tothat of the rotating mechanism 40 in the first embodiment. The rotatingmechanism 40 a is disposed on the right side of the center line CL incorrespondence with the positions of the connecting mechanisms 30 a and30 b, and the rotating mechanism 40 b are disposed on the left side ofthe center line CL in correspondence with the positions of theconnecting mechanisms 30 c and 30 d. The rotating mechanisms 40 a and 40b are disposed almost linearly symmetrically with respect to the centerline CL, and have almost linearly symmetric structures with respect tothe center line CL.

In addition, a guide member 16 a is provided on the right part of thesupporting portion 14 with respect to the center line CL incorrespondence with the connecting mechanisms 30 a and 30 b, and a guidemember 16 b is provided on the left part of the supporting portion 14with respect to the center line CL in correspondence with the connectingmechanisms 30 c and 30 d.

According to the screen unit 6, the connecting mechanisms 30 a and 30 bare expanded and contracted by the rotating mechanism 40 a, and theconnecting mechanisms 30 c and 30 d are expanded and contracted by therotating mechanism 40 b for expansion and storage of the screen 10.Thus, when the rotating mechanisms 40 a and 40 b are controlled suchthat they can rotate in synchronization with each other, the expansionand contract of the connecting mechanisms 30 a and 30 b and of theconnecting mechanisms 30 c and 30 d can be synchronized with each otherat the time of expansion and storage of the screen 10.

According to the structure of the screen unit 6 in the sixth embodiment,the flatness of the screen 10 does not lower even when the screen unithas a projection surface whose ratio of the length in the horizontaldirection (X direction) to the length in the vertical direction (Zdirection) is still larger.

In the screen unit 6, each of the rotating mechanisms 40 a and 40 b maybe replaced with the rotating mechanism 50A in the second embodiment orthe rotating mechanism 50B in the third embodiment.

The respective embodiments described herein may be modified in variousways without departing from the scope of the invention. For example, thefollowing modifications may be made.

Modified Example 1

While each of the screen units in the respective embodiments except forthe fourth embodiment expands and stores the screen by electric powerusing the electrically operated motor, the screen of the screen unit maybe manually expanded and stored by rotating a handle or the likeprovided on the rotation shaft without using the electrically operatedmotor. In this structure, lowering of the flatness of the screen 10 canbe prevented, and the screen can be expanded and stored in a stablecondition.

Modified Example 2

While each of the screen units in the respective embodiments includesthe connecting mechanisms each having two pairs of (four) or three pairsof (six) arms, the screen unit may include connecting mechanisms eachhaving a pair of (two) or four pairs of (eight) or a larger number ofarms. In these structures, advantages similar to those of the screenunits in the respective embodiments can be provided.

1. A screen unit comprising: a screen which has a first side and asecond side disposed opposed to each other and extending substantiallyin parallel with each other; a first supporting portion extending alongthe first side of the screen to support the first side; a secondsupporting portion extending along the second side of the screen tosupport the second side; and a plurality of connecting mechanisms eachof which extends between the first supporting portion and the secondsupporting portion, and expands and contracts in the direction in whichthe first supporting portion and the second supporting portion areopposed to move the second supporting portion close to and away from thefirst supporting portion, wherein the plurality of connecting mechanismsare disposed in parallel in the direction in which the first supportingportion and the second supporting portion extend, and are located almostlinearly symmetric with respect to a center line connectingapproximately the center of the first side in the extending direction ofthe first side and approximately the center of the second side in theextending direction of the second side.
 2. The screen unit according toclaim 1, wherein the plural connecting mechanisms include a plurality offirst connecting mechanisms disposed as a pair or pairs on both parts ofthe screen unit with the center line interposed therebetween.
 3. Thescreen unit according to claim 2, wherein the plural connectingmechanisms include a pair of the first connecting mechanisms; and thepair of the first connecting mechanisms have almost linearly symmetricstructures with respect to the center line as viewed in the normal linedirection of a projection surface of the screen.
 4. The screen unitaccording to claim 3, wherein the first supporting portion includes apair of fixed supports provided at predetermined positions and a pair ofmovable supports movable in the extending direction of the firstsupporting portion in correspondence with the pair of the firstconnecting mechanisms; the second supporting portion includes a pair offixed supports provided at predetermined positions and a pair of movablesupports movable in the extending direction of the second supportingportion in correspondence with the pair of the first connectingmechanisms; the respective first connecting mechanisms are connectedwith the respective fixed supports and the respective movable supportsof the first supporting portion and with the respective fixed supportsand the respective movable supports of the second supporting portion;and each pair of the fixed supports of the first supporting portion,each pair of the movable supports of the first supporting portion, eachpair of the fixed supports of the second supporting portion and eachpair of the movable supports of the second supporting portion aredisposed almost linearly symmetric with respect to the center line. 5.The screen unit according to claim 4, wherein the pair of the fixedsupports of each of the first supporting portion and the secondsupporting portion are disposed outside the pair of the movable supportsof the corresponding supporting portion with respect to the center line.6. The screen unit according to claim 5, further comprising: a rotatingmechanism which has a rotation shaft extending along the firstsupporting portion, wherein each of the pair of the movable supports ofthe first supporting portion has a screw portion which has a femalescrew formed coaxially with each other, the rotation shaft is insertedthrough the screw portions of the pair of the movable supports of thefirst supporting portion and has a male screw engaging with the screwportions, and one of the screw portions of the pair of the movablesupports is a right-handed screw, and the other of the screw portions ofthe pair of the movable supports is a left-handed screw.
 7. The screenunit according to claim 5, further comprising: a rotating mechanismwhich has a rotation shaft disposed between the pair of the movablesupports of the first supporting portion, wherein one of the pair of themovable supports is connected with the rotation shaft via a first wire,and the other of the pair of the movable supports is connected with therotation shaft via a second wire, and the first wire and the second wireare wound or returned in accordance with the rotation direction of therotation shaft to shift the pair of the movable supports in directionsopposite to each other along the first supporting portion.
 8. The screenunit according to claim 6, wherein the rotating mechanism has anelectrically operated motor which rotates the rotation shaft.
 9. Thescreen unit according to claim 2, wherein the plural connectingmechanisms further include a second connecting mechanism disposed on thecenter line.